1. Field of the Invention
The present invention relates to a directly motor-driven spindle assembly for spinning machines, such as spinning frames and twisting frames, having a spindle blade securely restrained from jumping up.
2. Description of the Prior Art
Various means for restraining a spindle blade from jumping up have been proposed.
A first prior art disclosed in Japanese Patent Laid-open (Kokai) No. 64-52825 utilizes permanent magnets for attracting a rotary unit to a fixed unit by magnetic attraction.
A second prior art disclosed in Japanese Patent Laid-open (Kokai) No. 60-139153 employs a mechanism capable of generating a thrust by utilizing the axial component of force produced by the rotor with skew conductors of a motor.
The first prior art has no means for controlling the large vibration and jumping of the rotary unit; the magnetic attraction between the permanent magnets is reduced and become ineffective when the rotary unit jumps up a large distance.
Another prior art illustrates that the rotor of the motor of a sealed rotary compressor with skew conductors to generate a downward thrust and nothing is considered about generating a thrust according to an axial load on a rotary unit which rotates at a high speed. The axial component of force acts downward only when the rotary unit rotates in one direction and acts upward to promote the jumping up of the rotary unit when the rotary unit rotates in the opposite direction.